[PATCH 2/2] crypto: arm - add build time test for CRC instruction support

[ard.biesheuvel@linaro.org (Ard Biesheuvel)]

The accelerated CRC32 module for ARM may use either the scalar CRC32
instructions, the NEON 64x64 to 128 bit polynomial multiplication
(vmull.p64) instruction, or both, depending on what the current CPU
supports.

However, this also requires support in binutils, and as it turns out,
versions of binutils exist that support the vmull.p64 instruction but
not the crc32 instructions.

So refactor the Makefile logic so that this module only gets built if
binutils has support for both.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm/crypto/Makefile | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm/crypto/Makefile b/arch/arm/crypto/Makefile
index 1822c4697278..f2215fbeed13 100644
--- a/arch/arm/crypto/Makefile
+++ b/arch/arm/crypto/Makefile
@@ -15,7 +15,17 @@ ce-obj-$(CONFIG_CRYPTO_SHA1_ARM_CE) += sha1-arm-ce.o
 ce-obj-$(CONFIG_CRYPTO_SHA2_ARM_CE) += sha2-arm-ce.o
 ce-obj-$(CONFIG_CRYPTO_GHASH_ARM_CE) += ghash-arm-ce.o
 ce-obj-$(CONFIG_CRYPTO_CRCT10DIF_ARM_CE) += crct10dif-arm-ce.o
-ce-obj-$(CONFIG_CRYPTO_CRC32_ARM_CE) += crc32-arm-ce.o
+crc-obj-$(CONFIG_CRYPTO_CRC32_ARM_CE) += crc32-arm-ce.o
+
+ifneq ($(crc-obj-y)$(crc-obj-m),)
+ifeq ($(call as-instr,.arch armv8-a\n.arch_extension crc,y,n),y)
+ce-obj-y += $(crc-obj-y)
+ce-obj-m += $(crc-obj-m)
+else
+$(warning These CRC Extensions modules need binutils 2.23 or higher)
+$(warning $(crc-obj-y) $(crc-obj-m))
+endif
+endif
 
 ifneq ($(ce-obj-y)$(ce-obj-m),)
 ifeq ($(call as-instr,.fpu crypto-neon-fp-armv8,y,n),y)
-- 
2.7.4